I have. It's more of less a minimalistic firefox browser that you can run in its own instance from the desktop. I will call it super bookmarking. But this doesn't solve the problem the poster is writing about. You still have to login to sites and deal with visual inconsistencies. What I think he wants is the equivalent of iPhone apps, where you pay or download for free, that have a consistent UI and are built to be simple, familiar and to the point.

The iPhone apps I have played with up to this point have done exactly that. No nagging for logins or registration. If you had to do it once, that was it and you never hear about it again. They get you right to what you are looking for and its familiar.